This invention relates to a system including a motor and other actuator driving power amplifiers other than a circuit system, and is particularly concerned with a circuit for compounding functions of DC power, DC amplification and AC amplification for, improving the motor power efficiency and thus preferably for realizing miniaturization and lighter weight requirements and also for enhancing economical efficiency of the system as a whole.
In a prior art DC to DC converter, a great interest has been taken particularly in a stabilization of a plurality of DC outputs as disclosed in Japanese Patent Laid-Open No. 140153/1979 and also illustrated in FIG. 5-16, p. 154 to FIG. 5-20, p. 157 representing examples of a multi-power circuit given in Paragraph 5.4, "Knowhow on Engineering Switching Regulator" by Hasegawa, Published by CQ Publishing Co. Roughly speaking, however, a power unit and an amplifier and other apparatuses operating from a power fed from the supply are fabricated separately from each other in a conventional design and development, and an improvement has been provided in each field accordingly. Consequently, there is no unifying idea common to both systems the two and thus to regard as a new system to improvement like the invention. That is, the prior art DC to DC converter described as above is used exclusively for obtaining direct current or pulsating current output. The multi-channel outputting is only to obtain a plurality of supply DC outputs, and outputs modulated independently from other outputs. Another modulating DC to DC converter or inverter or power amplifier and the like is connected further to output side. Accordingly, when modulating a multiplicity of output channels independently of each other, a drawback is inevitable such that the system enlarges in size entirely, and the cost increases considerably.
Further in the prior art, the output is limited only to a direct current, No consideration has been paid to outputting an alternating current instead of the direct current output, and thus a power circuit is intended only as direct current output power.
Still further, there is a problem resulting with the known example described in the foregoing Japanese Patent Laid-Open No. 140153/1979 as referred to in FIG. 1.
That is, in FIG. 1, a DC voltage is impressed on a primary coil inductance (hereinafter shortened to "primary inductance") 2-1 of a transformer 2 from a primary supply 1 through a switching element 3 such as a transistor or the like. The switching element 3 operates in an on/off manner according to a switching control circuit 13, and a voltage pulse is generated on secondary coil inductances (hereinafter shortened to "secondary inductances") 2-2, 2-3 of the transformer 2 at a duty ratio equal to the on/off duty ratio of the switching element 3. An amplitude of the voltage pulse is determined on a winding ratio of the primary coil 2-1 to the secondary coils 2-2, 2-3. The voltage pulse generated on the secondary coil 2-2 is rectified by a diode 4-1, smoothed by a capacitor 5-1 to a DC voltage, and is fed to a load 6 or a circuit system, for example, as power supply voltage. Then, the voltage pulse generated on the secondary coil 2-3 is also rectified by a diode 4-2, smoothed by a capacitor 5-2 to a DC voltage, and is fed to a servo circuit 8 controlling a servomotor 7 as a supply voltage. The ratio of a power supply voltage impressed on the load 6 to the supply voltage impressed on the servo circuit 8 is determined on a winding ratio of the secondary coils 2-2, 2-3 of the transformer 2. The servo circuit 8 makes a voltage impressed on the servomotor 7 variable according to a control signal from an input terminal 9, thus controlling rotational quantity, rotational speed and others of the servomotor 7.
Meanwhile, a supply voltage impressed on the load 6 or circuit system must be constant, and even if the voltage impressed on the servomotor 7 is made variable, a supply voltage impressed on the load including the servomotor 7 and the servo circuit 8 must also be constant.
Now, therefore, the supply voltage impressed on the servo circuit 8 is also fed to an error amplifier 10 and compared with a reference voltage from a reference supply 11 with an amplitude equal to the amplitude to be set by the supply voltage. If there is a difference between the two, then the error voltage is fed to a switching control circuit 13 through a coupling element 12 consisting of photocoupler, transformer and other elements. The switching control circuit 13 changes the on/off duty ratio of the switching element 3 according to the error voltage. Thus, the supply voltage impressed on the servo circuit 8 is fixed to a normal amplitude, and the supply voltage impressed on the load 6 constant in ratio therewith is also fixed to a normal amplitude.
Then, an amplitude of the reference voltage of the reference supply 11 will be set equal to the normal amplitude of the supply voltage impressed on the load 6, and the reference voltage may be compared with the supply voltage impressed on the load 6 by the error amplifier 10.
Thus the above-described prior art comprises regulating output supply voltages to each load so as not to fluctuate unevenly but to stabilize equally. As the load, the supply voltage must not only be kept constant at all times like a circuit system but may also be changed, as occasion demands, to a control action. For example, in the case of servomotor 7 of FIG. 1, the supply voltage will be made controllable on a control signal and if the supply voltage can be impressed directly on the motor 7, then the servo circuit 8 with a heavy power consumption can be omitted.
However, in the prior art shown in FIG. 1, since each output supply voltage is kept constant, a servo circuit with heavy power consumption will be required for the load for which an impressed voltage must be made variable, and thus while a power loss in the power circuit is to be decreased by a switching operation, a construction to increase the power loss on a load is quite unavoidable.